Fix for #2445 (book read status can't be set if custom column is linked and read status was set before)

cps/helper.py

@@ -322,12 +322,12 @@ def edit_book_read_status(book_id, read_status=None):
         try:
             calibre_db.update_title_sort(config)
             book = calibre_db.get_filtered_book(book_id)
-            read_status = getattr(book, 'custom_column_' + str(config.config_read_column))
-            if len(read_status):
+            book_read_status = getattr(book, 'custom_column_' + str(config.config_read_column))
+            if len(book_read_status):
                 if read_status is None:
-                    read_status[0].value = not read_status[0].value
+                    book_read_status[0].value = not book_read_status[0].value
                 else:
-                    read_status[0].value = read_status is True
+                    book_read_status[0].value = read_status is True
                 calibre_db.session.commit()
             else:
                 cc_class = db.cc_classes[config.config_read_column]